Electronic devices are becoming more and more portable. One portable form factor of particular interest is referred to as a “wrist-worn” device. Many different types of devices can be incorporated into a wrist-worn device form factor including, for example, a display device, a communication device and other devices. If the device is a communication device, it generally includes an antenna system for transmitting and/or receiving a communication signal.
In a small wrist-worn communication device, antenna design is very challenging due to factors such as device size, the material or materials from which the device is fabricated, orientation of the device during use, proximity of the device to an individual wearing the device, and other factors. These factors are also applicable to devices other than wrist-worn devices, such as tablet and other hand-held computing and electronic devices.
One factor of particular interest is that a metallic structure included in many of the above mentioned devices inhibits the ability of the antenna to properly radiate and receive electromagnetic energy. Such a metallic structure could be a bezel, a bracelet, a cuff, a band or another metallic structure. The extent of degradation in performance is directly related to the proximity of the antenna to the metallic structure. A metal ring or loop shaped structure in a wrist-worn or other device can significantly degrade the performance of an antenna located inside of the device. As a result there is a tradeoff between antenna design and industrial/mechanical design because antenna design dictates the absence of any metallic ring or loop shaped component in the device, but such a ring or loop shaped component may be desired in such a device for aesthetic purposes.
It is possible to use such a metallic structure as an antenna if the ring or loop shaped structure is non-continuous so that the length of the antenna can be controlled so as to correspond to a wavelength of a communication signal at a desired frequency. Unfortunately, there are many instances where it is not possible to separate the ring or loop structure into a non-continuous element.
Therefore, it would be desirable to have a way of using a continuous metallic ring or loop shaped component in a wrist-worn or other portable device as an antenna.